24. Epilobium coloratum Biehler, Pl. Nov. Herb. Spreng. 18. 1807.
Epilobium coloratum var. tenuifolium H. H. Eaton; E. domingense Urban
Herbs often robust and rank, with sessile or short-stalked leafy basal rosettes and dense fibrous roots. Stems erect, subterete, (20–)40–85(–120) cm, freely branched distally, subglabrous proximal to inflorescence, often with raised strigillose lines decurrent from petioles, densely strigillose distally. Leaves opposite proximal to inflorescence, alternate distally, petiole 4–10 mm; blade narrowly lanceolate to lanceolate or narrowly elliptic, 3–10(–15) × 0.5–3 cm, subequal to internodes, base rounded to cuneate, margins sharply and irregularly serrulate, 30–75 teeth per side, veins prominent, often raised abaxially, 10–25 per side, apex acute or acuminate, surfaces subglabrous with strigillose margins and abaxial veins; bracts abruptly reduced. Inflorescences usually upright panicles, sometimes corymbiform, rarely racemes, densely strigillose. Flowers erect; buds 2–3 × 1.5–2.5 mm; pedicel 5–10 mm; floral tube 0.3–0.6 × 0.3–0.5 mm, raised ring of sparse spreading hairs at mouth inside; sepals 1.3–3.2 × 0.5–1.5 mm, abaxial surface strigillose; petals white, 2.5–5.5 × 2–3.8 mm, apical notch 0.5–1 mm; filaments white, those of longer stamens 1.8–2.5 mm, those of shorter ones 1.5–2 mm; anthers pale yellow, 0.3–0.4 × 0.2–0.4 mm; ovary 15–30 mm, ± densely strigillose; style erect, white, 1.5–2.8 mm, glabrous, stigma cylindrical to subcapitate, entire, 1–1.5 × 0.8–1.2 mm, surrounded by longer anthers. Capsules 40–65 mm, surfaces strigillose; pedicel 8–12 mm. Seeds narrowly oblanceoloid, 1.2–1.7 × 0.3–0.5 mm, abruptly rounded with very short chalazal neck, brownish gray, surface evenly papillose; coma not easily detached, cinnamon red, 8–12 mm. 2n = 36.
Flowering Jul–Sep. Saturated swampy areas, stream banks in lowland forests, wet ditches, open, disturbed wetlands, secondary floodplain forests; 0–500(–1500) m; N.B., Nfld. and Labr. (Nfld.), N.S., Ont., Que.; Ala., Ariz., Ark., Conn., Del., D.C., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Mo., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Okla., Pa., R.I., S.C., S.Dak., Tenn., Tex., Vt., Va., W.Va., Wis.; West Indies (Dominican Republic, Haiti).
Epilobium coloratum is highly unusual in having a distribution primarily in southeastern North America. In its overall morphology, particularly leaves and flowers, it more closely resembles European species such as E. obscurum Schreber or E. tetragonum Linnaeus than any other North American species, and shares with the European species the widespread BB chromosome arrangement. There is a general resemblance between E. coloratum and the very widespread E. ciliatum (AA chromosome arrangement); hybrids between these species, known as E. ×wisconsinense Ugent, are highly sterile due to different chromosome arrangements in the parental species. The true affinities of E. coloratum are uncertain. Its occurrence on Hispaniola is also unique and possibly due to a recent introduction.
Prior to 1950, all major treatments of Epilobium attributed the name of E. coloratum to Muhlenberg (as E. coloratum Muhlenberg ex Wildenow), including C. Haussknecht (1884), W. Trelease (1891), and others. However, M. L. Fernald (1945d) noted that Index Kewensis had overlooked the 1807 publication by Biehler and virtually all treatments since that time follow the interpretation by Fernald.